1 /*
2 * Copyright (C) 2022 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "src/traced/probes/ftrace/ftrace_print_filter.h"
18
19 #include <string.h>
20
21 #include "protos/perfetto/config/ftrace/ftrace_config.gen.h"
22 #include "src/traced/probes/ftrace/event_info_constants.h"
23
24 namespace perfetto {
25 namespace {
26 using ::perfetto::protos::gen::FtraceConfig;
27
PrefixMatches(const std::string & prefix,const char * start,size_t size)28 bool PrefixMatches(const std::string& prefix, const char* start, size_t size) {
29 if (prefix.size() > size) {
30 return false;
31 }
32 return strncmp(prefix.c_str(), start, prefix.size()) == 0;
33 }
34
AtraceMessageMatches(const std::string & before_pid_part,const std::string & after_pid_prefix,const char * start,size_t size)35 bool AtraceMessageMatches(const std::string& before_pid_part,
36 const std::string& after_pid_prefix,
37 const char* start,
38 size_t size) {
39 base::StringView s(start, size);
40 if (!s.StartsWith(base::StringView(before_pid_part))) {
41 return false;
42 }
43 s = s.substr(before_pid_part.size());
44
45 if (!s.StartsWith("|")) {
46 return false;
47 }
48 s = s.substr(1);
49
50 size_t skip_pid_count = 0;
51 for (;; skip_pid_count++) {
52 if (skip_pid_count == s.size()) {
53 return false;
54 }
55 if (s.at(skip_pid_count) == '|') {
56 break;
57 }
58 if (!isdigit(s.at(skip_pid_count))) {
59 return false;
60 }
61 }
62 skip_pid_count++;
63 s = s.substr(skip_pid_count);
64
65 return PrefixMatches(after_pid_prefix, s.data(), s.size());
66 }
67
68 } // namespace
69
70 // static
RuleMatches(const Rule & rule,const char * start,size_t size)71 bool FtracePrintFilter::RuleMatches(const Rule& rule,
72 const char* start,
73 size_t size) {
74 switch (rule.type) {
75 case Rule::Type::kAtraceMessage:
76 return AtraceMessageMatches(rule.before_pid_part, rule.prefix, start,
77 size);
78 case Rule::Type::kPrefixMatch:
79 break;
80 }
81 return PrefixMatches(rule.prefix, start, size);
82 }
83
FtracePrintFilter(const FtraceConfig::PrintFilter & conf)84 FtracePrintFilter::FtracePrintFilter(const FtraceConfig::PrintFilter& conf) {
85 rules_.reserve(conf.rules().size());
86 for (const FtraceConfig::PrintFilter::Rule& conf_rule : conf.rules()) {
87 Rule rule;
88 rule.allow = conf_rule.allow();
89 if (conf_rule.has_atrace_msg()) {
90 rule.type = Rule::Type::kAtraceMessage;
91 rule.before_pid_part = conf_rule.atrace_msg().type();
92 rule.prefix = conf_rule.atrace_msg().prefix();
93 } else {
94 rule.type = Rule::Type::kPrefixMatch;
95 rule.prefix = conf_rule.prefix();
96 }
97 rules_.push_back(std::move(rule));
98 }
99 }
100
IsAllowed(const char * start,size_t size) const101 bool FtracePrintFilter::IsAllowed(const char* start, size_t size) const {
102 for (const Rule& rule : rules_) {
103 if (RuleMatches(rule, start, size)) {
104 return rule.allow;
105 }
106 }
107 return true;
108 }
109
110 // static
Create(const protos::gen::FtraceConfig::PrintFilter & config,ProtoTranslationTable * table)111 std::optional<FtracePrintFilterConfig> FtracePrintFilterConfig::Create(
112 const protos::gen::FtraceConfig::PrintFilter& config,
113 ProtoTranslationTable* table) {
114 const Event* print_event = table->GetEvent(GroupAndName("ftrace", "print"));
115 if (!print_event) {
116 return std::nullopt;
117 }
118 const Field* buf_field = nullptr;
119 for (const Field& field : print_event->fields) {
120 if (strcmp(field.ftrace_name, "buf") == 0) {
121 buf_field = &field;
122 break;
123 }
124 }
125 if (!buf_field) {
126 return std::nullopt;
127 }
128
129 if (buf_field->strategy != kCStringToString) {
130 return std::nullopt;
131 }
132 FtracePrintFilterConfig ret{FtracePrintFilter{config}};
133 ret.event_id_ = print_event->ftrace_event_id;
134 ret.event_size_ = print_event->size;
135 ret.buf_field_offset_ = buf_field->ftrace_offset;
136 return std::move(ret);
137 }
138
FtracePrintFilterConfig(FtracePrintFilter filter)139 FtracePrintFilterConfig::FtracePrintFilterConfig(FtracePrintFilter filter)
140 : filter_(filter) {}
141
IsEventInteresting(const uint8_t * start,const uint8_t * end) const142 bool FtracePrintFilterConfig::IsEventInteresting(const uint8_t* start,
143 const uint8_t* end) const {
144 PERFETTO_DCHECK(start < end);
145 const size_t length = static_cast<size_t>(end - start);
146
147 // If the end of the buffer is before the end of the event, give up.
148 if (event_size_ >= length) {
149 PERFETTO_DFATAL("Buffer overflowed.");
150 return true;
151 }
152
153 const uint8_t* field_start = start + buf_field_offset_;
154 return filter_.IsAllowed(reinterpret_cast<const char*>(field_start),
155 static_cast<size_t>(end - field_start));
156 }
157
158 } // namespace perfetto
159